The invention relates to the field of micro-electro-mechanical systems (MEMS), and in particular a new actuation technique for MEMS switching that injects the energy required to actuate a switch over a number of mechanical oscillation cycles rather than just one.
In MEMS parallel plate and torsional actuators, the pull-in phenomenon has been effectively utilized as a switching mechanism for a number of applications. Pull-in is the term that describes the snapping together of a parallel plate actuator due to a bifurcation point that arises from the nonlinearities of the system. Typically the analysis of the pull-in phenomena is performed using quasi-static assumptions. However, it has been shown that under dynamic conditions, the pull-in voltage can be different from what the quasi-static analysis predicts. In a torsional switch, the pull-in voltage is found to be 8V when the voltage is slowly ramped up whereas when the voltage is applied as a step function, the pull-in voltage is only 7.3V.
Micro-electro-mechanical system (MEMS) switches based on parallel plate electrostatic actuators have demonstrated impressive performance in applications such as RF and low frequency electronic switching as well as optical switching. However, these devices have not yet become significantly commercialized. One of the reasons for this is that these switches tend to have operating voltages higher than what is normally available from an integrated circuit. Voltage up-converters are therefore necessary for these devices to operate in commercial applications which add cost, complexity, and power consumption. While some electrostatic MEMS switches have been designed for low voltage operation by decreasing the structure stiffness, this has so far only been with a significant sacrifice in reliability and performance. There are other actuation techniques, such as thermal or magnetic, that operate with lower voltages, however these are significantly slower than electrostatic switches and also consume much more power.